The present invention relates to a film depositing apparatus for forming a film on a surface of an elongated substrate in vacuum by CVD and, more particularly, to a film depositing apparatus which, when forming a film continuously on the elongated substrate as it is transported, is capable of forming a film having high uniformity in thickness in the direction of width of the substrate that is perpendicular to its longitudinal direction.
While various types of apparatus are known to be capable of continuous film deposition on an elongated substrate (a web of substrate) in a vacuum-filled chamber by plasma-enhanced CVD, an exemplary system uses a drum electrically connected to the ground and an electrode positioned in a face-to-face relationship with the drum and connected to a radio-frequency power source.
In this type of film depositing apparatus, the substrate is wrapped around a specified area of the drum, which is then rotated to thereby transport the substrate in a longitudinal direction as it is in registry with a specified film depositing position, with a radio-frequency voltage being applied between the drum and the electrode to form an electric field while, at the same time, a feed gas for film deposition as well as argon gas and the like are introduced between the drum and the electrode, whereby a film is deposited on the surface of the substrate by plasma-enhanced CVD. This type of film depositing apparatus has already been proposed (see JP 2006-152416 A).
JP 2006-152416 A discloses an apparatus for plasma-enhanced CVD that comprises a reaction compartment, gas inlets through which reactive gases are introduced into the reaction compartment, an anode and a cathode electrode that are provided within the reaction compartment to generate plasma discharge between themselves, and a transport mechanism that transports a flexible substrate between the anode and the cathode electrode; the apparatus treats the flexible substrate by plasma-enhanced CVD.
The reaction compartment has four gas discharging units for discharging the gas from the inside (see FIG. 1 in JP 2006-152416 A) and each gas discharging unit is equipped with a vacuum pump such as a mechanical booster pump or a rotary pump.
The anode electrode has a curved, first discharge surface whereas the cathode electrode has a second discharge surface that is curved along the first discharge surface. The cathode electrode is provided with an electrode-to-electrode distance adjusting mechanism for moving it in a direction parallel to the diameter of the anode electrode, as well as a curvature adjusting mechanism for performing fine adjustment on the curvature of the second discharge surface in accordance with the distance between the anode and cathode electrodes.